The present invention relates to copper-containing amine polymers, to a process for their preparation, and to their use as fungicides.
The use of copper salts in agriculture for the control of fungal diseases in crop plants is a practice of long-standing. To ensure the effectiveness of a copper treatment over a prolonged period, inorganic copper salts like copper oxychloride have been used which are sparingly soluble or insoluble in water. Oily formulations of copper salts based on low-molecular organic carboxylic acids have also been disclosed; these formulations have an activity comparable to the inorganic copper salts but a considerably lower copper content, and are less suitable for the treatment of plants because of their oily basis.
The art has therefore developed fungicidal agents in which copper salts of organic acids, which are themselves only sparingly soluble in water, are brought into aqueous solution by complex-formation with ammonia, as described in West German Offenlegungsschriften No. 2,807,293 and No. 2,202,448, in U.S. Pat. No. 3,900,504, and in British patent specifications No. 599,443 and No. 593,416. When these aqueous solutions are applied to the surfaces to be treated, particularly to crop plants, the ammonia evaporates along with the solvent; as a result, the sparingly soluble copper salts are reformed on the treated surface, effecting a slow release of copper ions and, hence, a persistent fungicidal action.
But these salts display only a poor adhesion to the plant surfaces, in the extent that they are washed off in solid form (although not dissolved) by rain. Accordingly, the literature cited above limits the suitability of these substances as fungicides mainly to the treatment of textiles and wood, with no mention of their suitability for plant protection.
Copper salts displaying better adhesion are obtained, in accordance wtih British patent specification No. 1,394,990 and European patent application No. 0 039 788, by converting copper salts of polycarboxylic acids (acrylic acid or methacrylic acid polymers) into water-soluble, complex compounds by treatment with ammonia, and then applying them in complexed form. Once again, evaporation of the ammonia results in the reformation, on the leaf surface, of the sparingly soluble copper salt, from which copper ions having a fungicidal action are slowly released. It is a disadvantage of these solutions that a considerable excess of ammonia has to be added to achieve adequate complexing of the copper ions; consequently, the solutions effect a strongly alkaline reaction and damage the plants when applied. Moreover, a considerable odor nuisance arises through the evaporation of the ammonia.
Synthetic resins containing copper bound as a complex can be prepared from Mannich bases, free from epoxide groups, and have been used as pigments, curing catalysts, antifoaming agents and adhesion promoters (see West German Offenlegungsschrift No. 3,045,251). But no information has been available regarding their use as fungicides.